In order to establish standing, Keyes still has to show an injury in fact that is real and concrete, not hypothetical or conjectural. So if Obama is in fact unqualified, how does that cause Keyes damage? That's the hurdle that all these cases are having problems surmounting.
According to Taitz/Kreep, they claim that Keyes and his list of Electors have standing under CA law. Every state law is different, there is no universal ‘law of standing’ across 50 states. These cases are being filed against Secretaries of States under state laws.
You didn’t respond to part about the McCain Electors having been harmed in states where Obama won. Under some state laws such as my state of NY, those Electors don’t have standing. But under other state laws they do.